Pipe coupling thermal cleaning and coating curing oven and method

ABSTRACT

Systems and methods for treating metal pipe couplings, including a frame and insulated panels attached to the frame forming an oven. A pre-heat zone and a bake zone inside the oven, the pre-heat zone separated from the bake zone by a shared oven wall. A combustion burner and recirculation blower are positioned in opposite ends of the oven in a pre-heat zone combustion/recirculation chamber. Another burner and recirculation blower pair are positioned in opposite ends of the oven in a bake zone combustion/recirculation chamber. Heated air supply plenums are fluidly connected to respective recirculation blowers, and include direction-adjustable nozzles to direct heated air generally downward onto pipe couplings moving through the preheat and bake zones. Return air plenums positioned in each of the pre-heat and bake zones each have an air inlet, and an outlet fluidly connected to respective combustion/recirculation chambers. Coating-cured metal pipe couplings made by the methods.

BACKGROUND INFORMATION

Technical Field

The present disclosure relates generally to the field of pipe couplingtreatment systems, and methods of use, and more specifically to pipecoupling ovens thermal cleaning and coating ovens (systems), and methodsof their use, particularly for producing internal or externally coatedpipe couplings.

Background Art

It is a common practice to coat and apply protective coatings to pipesof all sorts, such as line pipes, which are buried underground, to movegasses or liquids from point A to point B. The pipe may have diameteranywhere from 2 inches, all the way to 48 inches or more and have eitherinternal or external coatings applied, depending on the application, forcorrosion protection or ease of flow. For example, line pipes and drillpipes typically have internal coated pipes to minimize friction for easyflow of fluids and have corrosion protection with the inner coating ofthe pipes. There are several service companies in the business ofapplying internal coatings to the pipes, including line pipes as well asthe drill pipes.

In a typical process, a phenolic coating is applied internally, andbaked on at 450-500° F. The process of coating the pipe, is typically asfollows:

-   -   First Stage: burn off the old coating or oils. Sometime termed        “pre-bake”, “burn off” or “pre-heat”, the pipe is heated to        750° F. to either burn off the old coatings on used pipe, or        burn off the oils on new pipe. This process is also sometimes        referred to as “thermal cleaning” of the pipe. One older        technique used to be to heat up the pipe in a burn off oven,        overnight, generally about 24 hours. Aziz Jamaluddin, one of the        inventors of the present patent application, and president of        Epcon® Industrial Systems, LP (formerly known as Entech        Industrial Systems) obtained several U.S. Pat. Nos. 4,240,787;        4,242,084, and 4,322,203, allowing this thermal cleaning process        to be reduced significantly in time.    -   Second stage: sand blasting. After thermal cleaning, the pipe is        internally sandblasted to white metal and then coatings are        applied in two to three stages, either liquid or powder.    -   Third stage: application of coating. The pipe from Stage 2 would        then roll into a separate conveyorized “bake” oven, two or three        in a row, each bake oven being preceded by an internal coating        station. The bake oven temperature is 400-500° F.    -   Fourth stage: the final bake.

Along with the pipe, there are pipe couplings of various sizes—anywherefrom 2.5 inch, 6 inch, 8 inch, 12 inch and up to 16 inch in diameter.Like the pipe, the couplings need to be thermally cleaned, typically attemperatures about 750° F., a coating is then applied, and then cured at450-500° F. This task is accomplished by putting the couplings in one ormore open containers or baskets inside the burnout oven and heating itfor several hours or overnight at 750° F., and then the next day thecouplings have the powder or liquid applied, and are then put in adifferent oven, operating at 450-500° F.

Various types of ovens and methods are used for the above, all generallycomprising a box or container defining a treatment zone, heatingapparatus such as burners for direct heating of circulating air, aircirculation fans, and exhaust fans. Due to the temperature differencebetween the thermal treatment and the coating bake steps, separate ovensare used. The above-mentioned '203 patent describes one such thermalcleaning oven, including an elongated rectangular framework supporting aplurality of insulated panels. The supporting framework comprises aplurality of vertically extending structural steel supports,longitudinally and horizontally extending supports, and laterally andhorizontally extending supports. The supports comprise steel H-beams orthe like and are preferably joined by welding into a rigid framework.The oven is enclosed by longitudinally extending, vertical side wallsconsisting of thick-walled insulated panels, and a longitudinallyextending top wall, consisting of a thick-walled insulated panel. Theoven is open at one end for introduction of pipe to be processed and hasa vertically sliding end door supported for vertical movement betweenvertical supporting H-beams. A pair of rails extend longitudinally ofthe oven which support the wheels of a cart for movement of a load ofpipe into and out of the oven. The oven chamber or enclosure issupported from the top portion of the frame, consisting of supports anda series of shorter, the vertically extending H-beam supports which alsosupport horizontally extending, bottom insulated panels. Obviously,these specifications can be varied, as needed, but represent a typicalcommercial installation. The oven has plenum chambers extendinglongitudinally thereof on opposite sides of the rails, each plenumchamber having a plurality of vertical slots or nozzles spaced along theentire length thereof for directing flow of heated air horizontally onto the pipe on the cart. The supply of heated air for heating the pipeto burnout temperature and the control of air pollution from the pipeburnout and recovery of waste energy are provided by equipment carriedon top of the supporting frame for the oven, including burners whichdraw air from the oven and heat it. The heated air is recirculated tothe oven by blowers. Air is exhausted slowly from the oven by an exhaustfan or blower through an incinerator, where hydrocarbon byproducts areconsumed. A heat exchanger is used to heat incoming combustion air forthe burner section. The air from the heat exchange section is exhaustedby the blower to atmosphere. The burner section comprises a rectangularchamber enclosed by insulated panels (the side walls, end walls, topwall, and bottom wall), the sidewalls having openings in which there arepositioned burners. The bottom wall of the burner chamber has a centralopening, which opens into the top of the elongated oven enclosure.

During most of the operation of oven of the '203 patent, the burnerchamber central opening is the only opening for circulation of air fromthe oven into burner chamber. End walls of the burner chamber haveopenings in which there are secured the inlet end and outlet end of aheat exchange conduit. This takes some of the heat away from thecombustion gases from the burner that otherwise could be used to heatthe pipe. The end walls of the combustion chamber also have openings forconnection to the inlet sides of the recirculation blowers, which inturn have their respective outlets connected by conduits to thevertical, oppositely opposed plenum chambers. The apparatus described inthe '203 patent is a batch type pipe burnout oven with air pollutioncontrol and heat recovery features.

As noted herein, the predominant technique is to employ separate ovensfor thermal cleaning and coating baking, employing direct-heated air incross-circulation flow of the air through pipes or couplings beingtreated, where flow direction of heated air onto the pipe or couplings(generally horizontal) is directed by side-mounted heated air plenums.While fairly efficient, this technique requires a lot of floor space dueto the use of separate ovens. This limits the applicability of thetechnique to operations where separate ovens are available, or to use ofthe same oven in different operating temperature regimes, which wouldalso be counterproductive.

It would be an advanced in the pipe coupling treatment art, and inparticular the art of combustion-based thermal cleaning and coatingbaking, to provide a more compact, conveyorized, simplified oven havingtwo or more treatment chambers, saving time, labor and space energyusage.

SUMMARY

In accordance with the present disclosure, apparatus, systems (ovens)and methods of treating raw metal pipe couplings and coated uncured pipecouplings using the apparatus and systems are described that may reduceor eliminate problems with known apparatus, systems, and methods.

One aspect of the disclosure is a method comprising (or consisting of,or consisting essentially of):

-   -   (a) continuously moving one or more raw metal pipe couplings        through a pre-heat zone of a structure for a time and        temperature sufficient to produce thermally cleaned pipe        couplings, and separately continuously moving thermally cleaned        pipe couplings having an uncured coating applied to at least a        portion thereof through a separate bake zone of the same        structure for a time and temperature sufficient to produce        coating-cured pipe couplings;    -   (b) forming a first hot fluid stream (preferably a hot        combustion product formed by directly heating air,        oxygen-enriched air, or oxidant) in a pre-heat zone hot fluid        (preferably combustion) chamber (preferably by directly heating        air, oxygen-enriched air, or oxidant injected into the pre-heat        zone combustion chamber by a first combustion burner), and        -   forming a second hot fluid stream (preferably a hot            combustion product formed by directly heated air,            oxygen-enriched air, or oxidant) in a bake zone hot fluid            (preferably combustion) chamber (preferably by directly            heating air, oxygen-enriched air, or oxidant injected into            the bake zone combustion chamber by a second combustion            burner);    -   (c) flowing the first and second hot fluid streams (preferably        combustion product streams, more preferably directly heated air        streams) into respective pre-heat zone and bake zone hot fluid        (preferably hot air) supply plenums, the pre-heat zone hot fluid        supply plenum positioned above the one or more raw metal pipe        couplings moving through the pre-heat zone, the bake zone hot        fluid supply plenum positioned above the one or more thermally        cleaned and uncured coated pipe couplings moving through the        bake zone;    -   (d) flowing the first and second hot fluid streams (preferably        combustion product streams, preferably directly heated air        streams) from respective hot fluid (hot air) supply plenums        generally vertically downward onto the respective pipe couplings        moving through the respective zones, the first and second hot        fluid (combustion product streams, preferably directly heated        air streams) flowing into and around the respective one or more        pipe couplings, and then exiting to left and right sides of the        respective zones, forming left and right pre-heat zone cooled        fluid (preferably cooled air) streams and left and right bake        zone cooled fluid (preferably cooled air) streams; and    -   (e) collecting a major portion of the left and right pre-heat        zone cooled fluid (preferably cooled air) streams in respective        left and right pre-heat zone return ducts, flowing the major        portion of the left and right pre-heat zone cooled fluid        (preferably cooled air) streams to the pre-heat zone hot fluid        (preferably combustion) chamber while venting (natural draft or        forced draft) a minor portion, and collecting a major portion of        the left and right bake zone cooled fluid (preferably cooled        air) streams in respective left and right bake zone return        ducts, flowing the major portion of the left and right bake zone        cooled fluid (preferably cooled air) streams to the bake zone        hot fluid (preferably combustion) chamber while venting (natural        draft or forced draft) a minor portion.

Another method embodiment comprises (or consists of, or consistsessentially of):

-   -   (a) continuously moving one or more raw metal pipe couplings        through a pre-heat zone of a structure for a time and        temperature sufficient to produce thermally cleaned pipe        couplings, and separately continuously moving thermally cleaned        pipe couplings having an uncured coating applied to at least a        portion thereof through a separate bake zone of the same        structure for a time and temperature sufficient to produce        coating-cured pipe couplings;    -   (b) forming a first heated air stream in a pre-heat zone        combustion chamber by directly heating air injected into the        pre-heat zone combustion chamber by a first combustion burner,        and        -   forming a second heated air stream in a bake zone combustion            chamber by directly heating air injected into the bake zone            combustion chamber by a second combustion burner;    -   (c) flowing the first and second heated air streams into        respective pre-heat zone and bake zone heated air supply        plenums, the pre-heat zone heated air supply plenum positioned        above the one or more raw metal pipe couplings moving through        the pre-heat zone, the bake zone heated air supply plenum        positioned above the one or more thermally cleaned and uncured        coated pipe couplings moving through the bake zone;    -   (d) flowing the first and second heated air streams from        respective heated air supply plenums generally vertically        downward onto the respective pipe couplings moving through the        respective zones, the first and second heated air streams        flowing into and around the respective one or more pipe        couplings, and then exiting to left and right sides of the        respective zones, forming left and right pre-heat zone cooled        air streams and left and right bake zone cooled air streams; and    -   (e) collecting a major portion of the left and right pre-heat        zone cooled air streams in respective left and right pre-heat        zone return ducts, flowing the major portion of the left and        right pre-heat zone cooled air streams to the pre-heat zone        combustion chamber while venting a minor portion, and collecting        a major portion of the left and right bake zone cooled air        streams in respective left and right bake zone return ducts,        flowing the major portion of the left and right bake zone cooled        air streams to the bake zone combustion chamber while venting a        minor portion.

Another aspect of the disclosure is a system comprising (or consistingessentially of, or consisting of):

-   -   (a) a platform, generally rectangular and having longitudinal        axis;    -   (b) a plurality of insulated panels attached to the platform and        defining sidewalls, a front end wall, a rear end wall, a        ceiling, and a bottom of an oven;    -   (c) a pre-heat zone and a bake zone inside the oven, the        pre-heat zone separated from the bake zone by a shared        (preferably central) internal vertical oven wall, non-insulated,        extending from the front end wall to the rear end wall, and from        the bottom to the ceiling of the oven;    -   (d) one or more pre-heat zone combustion burners and one or more        pre-heat zone recirculation blowers positioned in opposite ends        of the oven in a pre-heat zone combustion/recirculation chamber        positioned in an upper region of the pre-heat zone, and one or        more bake zone combustion burners and one or more bake zone        recirculation blowers positioned in opposite ends of the oven in        a bake zone combustion/recirculation chamber positioned in an        upper region of the bake zone;    -   (e) one or more pre-heat zone heated air supply plenums and one        or more bake zone heated air supply plenums, the plenums fluidly        connected to respective one or more of the recirculation        blowers, the heated air supply plenums comprising        direction-adjustable nozzles attached to a bottom panel thereof,        the heated air supply plenums positioned to direct heated air        through the nozzles and generally downward onto work pieces        traversing through the preheat and bake zones; and    -   (f) one or more return air plenums positioned generally        vertically in each of the pre-heat and bake zones, the one or        more return air plenums each having an air inlet below a level        of the bottom panels of the one or more heated air supply        plenums and an outlet fluidly connected to respective pre-heat        and post bake combustion/recirculation chambers.

Another system embodiment of this disclosure comprises (or consistsessentially of, or consists of):

-   -   (a) a platform, generally rectangular and having longitudinal        axis;    -   (b) a plurality of insulated panels attached to the platform and        defining left and right sidewalls, a front end wall, a rear end        wall, a ceiling, and a bottom of an oven;    -   (c) a pre-heat zone and a bake zone inside the oven, the        pre-heat zone separated from the bake zone by a shared internal        vertical oven wall, non-insulated, extending from the front end        wall to the rear end wall and centrally positioned between the        left and right sidewalls, and extending from the bottom to the        ceiling of the oven;    -   (d) one or more pre-heat zone combustion burners and one or more        pre-heat zone recirculation blowers positioned in opposite ends        of the oven in a pre-heat zone combustion/recirculation chamber        positioned in an upper region of the pre-heat zone, and one or        more bake zone combustion burners and one or more bake zone        recirculation blowers positioned in opposite ends of the oven in        a bake zone combustion/recirculation chamber positioned in an        upper region of the bake zone;    -   (e) one or more pre-heat zone heated air supply plenums and one        or more bake zone heated air supply plenums, the plenums fluidly        connected to respective one or more of the recirculation        blowers, the heated air supply plenums comprising        direction-adjustable nozzles attached to a bottom panel thereof,        the heated air supply plenums positioned to direct heated air        through the nozzles and generally downward onto work pieces        traversing through the preheat and bake zones;    -   (f) one or more return air plenums positioned generally        vertically in each of the pre-heat and bake zones, the one or        more return air plenums each having an air inlet below a level        of the bottom panels of the one or more heated air supply        plenums and an outlet fluidly connected to respective pre-heat        and post bake combustion/recirculation chambers; and    -   (g) separate first and second reversible conveyors positioned to        transport work pieces separately through the pre-heat zone and        bake zone.

Coating-cured pipe couplings made according to one of the methods ofthis disclosure are also considered within this disclosure.

Systems, apparatus, and methods of the disclosure will become moreapparent upon review of the brief description of the drawings, thedetailed description of the disclosure, and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the objectives of the disclosure and other desirablecharacteristics can be obtained is explained in the followingdescription and attached drawings in which:

FIG. 1 is a schematic process flow diagram of one method, system, andapparatus embodiment in accordance with the present disclosure;

FIGS. 2 and 3 are schematic right and left perspective views of one ovenembodiment in accordance with the present disclosure;

FIG. 4 is a schematic side elevation view of another oven embodiment inaccordance with the present disclosure;

FIGS. 5, 6, and 8 are schematic cross-sectional, plan and rear endelevation views, respectively, with portions cut away to show internalair flow patterns, of the embodiment of FIG. 4;

FIG. 7 is a detailed plan view of a conveyor roller set useful in thesystems and methods of the disclosure;

FIG. 9 is an exploded view of a nozzle and how it attaches to a heatedair or other heated fluid plenum panel using screws;

FIG. 10 is a detailed cross-section of a wall of the embodiment of FIGS.4-6 and 8; and

FIG. 11 is a logic diagram of one method embodiment of treating metalpipe couplings in accordance with the present disclosure.

It is to be noted, however, that the appended drawings are schematic innature, may not be to scale (in particular FIGS. 2-10), and illustrateonly typical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the disclosed systems, apparatus, and methods.However, it will be understood by those skilled in the art that thesystems, apparatus, and methods covered by the claims may be practicedwithout these details and that numerous variations or modifications fromthe specifically described embodiments may be possible and are deemedwithin the claims. For example, wherever the term “comprising” is used,embodiments and/or components and or steps where “consisting essentiallyof” and “consisting of” are explicitly disclosed herein and are part ofthis disclosure. All published patent applications and patentsreferenced herein are hereby explicitly incorporated herein byreference. In the event definitions of terms in the referenced patentsand applications conflict with how those terms are defined in thepresent application, the definitions for those terms that are providedin the present application shall be deemed controlling.

As explained briefly in the Background, the predominant technique is toemploy separate ovens for thermal cleaning and coating baking, employingdirect-heated air in cross-circulation flow of the air through pipes orcouplings being treated, where flow direction of heated air onto thepipe or couplings (generally horizontal) is directed by side-mountedheated air plenums. While fairly efficient, this technique requires alot of floor space due to the use of separate ovens. This limits theapplicability of the technique to operations where separate ovens areavailable, or to use of the same oven in different operating temperatureregimes, which would also be counterproductive.

It would be an advanced in the pipe coupling treatment art, and inparticular the art of combustion-based thermal cleaning and coatingbaking, to provide a more compact, conveyorized, simplified oven havingtwo or more treatment chambers, saving time, labor and space energyusage. The present application is devoted to resolving one or more ofthese challenges.

One aspect of the disclosure is a method comprising (or consisting of,or consisting essentially of):

-   -   (a) continuously moving one or more raw metal pipe couplings        through a pre-heat zone of a structure for a time and        temperature sufficient to produce thermally cleaned pipe        couplings, and separately continuously moving thermally cleaned        pipe couplings having an uncured coating applied to at least a        portion thereof through a separate bake zone of the same        structure for a time and temperature sufficient to produce        coating-cured pipe couplings;    -   (b) forming a first hot fluid stream (preferably a hot        combustion product formed by directly heating air,        oxygen-enriched air, or oxidant) in a pre-heat zone hot fluid        (preferably combustion) chamber (preferably by directly heating        air, oxygen-enriched air, or oxidant injected into the pre-heat        zone combustion chamber by a first combustion burner), and        -   forming a second hot fluid stream (preferably a hot            combustion product formed by directly heated air,            oxygen-enriched air, or oxidant) in a bake zone hot fluid            (preferably combustion) chamber (preferably by directly            heating air, oxygen-enriched air, or oxidant injected into            the bake zone combustion chamber by a second combustion            burner);    -   (c) flowing the first and second hot fluid streams (preferably        combustion product streams, more preferably directly heated air        streams) into respective pre-heat zone and bake zone hot fluid        (preferably hot air) supply plenums, the pre-heat zone hot fluid        supply plenum positioned above the one or more raw metal pipe        couplings moving through the pre-heat zone, the bake zone hot        fluid supply plenum positioned above the one or more thermally        cleaned and uncured coated pipe couplings moving through the        bake zone;    -   (d) flowing the first and second hot fluid streams (preferably        combustion product streams, preferably directly heated air        streams) from respective hot fluid (hot air) supply plenums        generally vertically downward onto the respective pipe couplings        moving through the respective zones, the first and second hot        fluid (combustion product streams, preferably directly heated        air streams) flowing into and around the respective one or more        pipe couplings, and then exiting to left and right sides of the        respective zones, forming left and right pre-heat zone cooled        fluid (preferably cooled air) streams and left and right bake        zone cooled fluid (preferably cooled air) streams; and    -   (e) collecting a major portion of the left and right pre-heat        zone cooled fluid (preferably cooled air) streams in respective        left and right pre-heat zone return ducts, flowing the major        portion of the left and right pre-heat zone cooled fluid        (preferably cooled air) streams to the pre-heat zone hot fluid        (preferably combustion) chamber while venting (natural draft or        forced draft) a minor portion, and collecting a major portion of        the left and right bake zone cooled fluid (preferably cooled        air) streams in respective left and right bake zone return        ducts, flowing the major portion of the left and right bake zone        cooled fluid (preferably cooled air) streams to the bake zone        hot fluid (preferably combustion) chamber while venting (natural        draft or forced draft) a minor portion.

Certain methods of this disclosure include those wherein the hot fluidstreams may be hot combustion products, and the hot fluid chambers arecombustion chambers, and the hot combustion products may be formed bycombusting one or more fuels with one or more oxidants in one or morecombustion burners attached to the structure externally of therespective combustion chambers, the one or more combustion burnersexhausting directly into the respective combustion chambers.

Certain methods of this disclosure include those wherein the forming afirst hot combustion product comprises forming a directly heated air,oxygen-enriched air, or oxidant stream in the pre-heat zone combustionchamber by directly heating air, oxygen-enriched air, or oxidantinjected into the pre-heat zone combustion chamber by a first combustionburner, and the forming a second hot combustion product comprisesforming a directly heated air, oxygen-enriched air, or oxidant stream inthe bake zone combustion chamber by directly heating air,oxygen-enriched air, or oxidant injected into the bake zone combustionchamber by a second combustion burner.

Certain methods of this disclosure include those wherein the fuel may benatural gas, the oxidant may be air, and the first and second hotcombustion product streams may be first and second directly heated airstreams.

In certain methods of this disclosure any one of, or any combination of,steps (b)-(e) may be continuous and carried out simultaneously with step(a). Certain methods of this disclosure include those wherein step (a)may comprise continuously moving one or more raw metal pipe couplingsthrough the pre-heat zone of the structure horizontally, and separatelycontinuously moving the thermally cleaned pipe couplings having anuncured coating applied to at least a portion thereof through theseparate bake zone of the same structure horizontally, both continuousmovements being parallel to a longitudinal axis of the structure. Incertain methods the horizontal movements may be in opposite directions.

Certain methods of this disclosure include those wherein the venting ofthe minor portions may comprise exhausting minor portions of the cooledstreams at a rate and amount sufficient to maintain a negative pressurein and near inlet and outlet vestibules of the pre-heat and bake zones.

Certain methods of this disclosure include those wherein the fuel isselected from the group consisting of methane, gaseous natural gas,liquefied natural gas, propane, butane, hydrogen, steam-reformed naturalgas, atomized hydrocarbon oil, combustible powders, flowable solids,waste materials, slurries, and mixtures or other combinations thereof,and the oxidant is selected from the group consisting of air, gaseshaving the same molar concentration of oxygen as air, oxygen-enrichedair having 50 mole percent or more oxygen, industrial grade oxygen, foodgrade oxygen, and cryogenic oxygen.

Certain methods of this disclosure include those wherein the time andtemperature sufficient to produce thermally cleaned pipe couplingsranges from about 1 to about 4 hours at temperature ranging from about600° F. to about 800° F., and the time and temperature sufficient toproduce cured coatings ranges from about 1 to about 4 hours attemperature ranging from about 350° F. to about 550° F.

Certain methods of this disclosure include controlling thermal cleaningof the one or more pipe couplings by one or more control methodsselected from the group consisting of monitoring composition of thevented fluid from the pre-heat zone, temperature of the pre-heat zonecombustion chamber, temperature of raw pipe couplings moving though thepre-heat zone, fuel and/or oxidant flow rate to the one or more pre-heatzone combustion burners, rate of moving the raw pipe couplings thoughtthe pre-heat zone, and combinations thereof, and controlling baking ofthe coating of the one or more pipe couplings by one or more controlmethods selected from the group consisting of monitoring composition ofvented fluid from the bake zone, temperature of the bake zone combustionchamber, temperature of thermally cleaned and uncured coated pipecouplings moving though the bake zone, fuel and/or oxidant flow rate tothe one or more bake zone combustion burners, rate of moving thethermally cleaned uncured coated pipe couplings thought the bake zone,and combinations thereof.

Another method embodiment comprises (or consists of, or consistsessentially of):

-   -   (a) continuously moving one or more raw metal pipe couplings        through a pre-heat zone of a structure for a time and        temperature sufficient to produce thermally cleaned pipe        couplings, and separately continuously moving thermally cleaned        pipe couplings having an uncured coating applied to at least a        portion thereof through a separate bake zone of the same        structure for a time and temperature sufficient to produce cured        coatings;    -   (b) forming a first heated air stream in a pre-heat zone        combustion chamber by directly heating air injected into the        pre-heat zone combustion chamber by a first combustion burner,        and        -   forming a second heated air stream in a bake zone combustion            chamber by directly heating air injected into the bake zone            combustion chamber by a second combustion burner;    -   (c) flowing the first and second heated air streams into        respective pre-heat zone and bake zone heated air supply        plenums, the pre-heat zone heated air supply plenum positioned        above the one or more raw metal pipe couplings moving through        the pre-heat zone, the bake zone heated air supply plenum        positioned above the one or more thermally cleaned and uncured        coated pipe couplings moving through the bake zone;    -   (d) flowing the first and second heated air streams from        respective heated air supply plenums generally vertically        downward onto the respective pipe couplings moving through the        respective zones, the first and second heated air streams        flowing into and around the respective one or more pipe        couplings, and then exiting to left and right sides of the        respective zones, forming left and right pre-heat zone cooled        air streams and left and right bake zone cooled air streams; and    -   (e) collecting a major portion of the left and right pre-heat        zone cooled air streams in respective left and right pre-heat        zone return ducts, flowing the major portion of the left and        right pre-heat zone cooled air streams to the pre-heat zone        combustion chamber while venting a minor portion, and collecting        a major portion of the left and right bake zone cooled air        streams in respective left and right bake zone return ducts,        flowing the major portion of the left and right bake zone cooled        air streams to the bake zone combustion chamber while venting a        minor portion.

Another aspect of the disclosure is a system comprising (or consistingessentially of, or consisting of):

-   -   (a) a platform, generally rectangular and having longitudinal        axis;    -   (b) a plurality of insulated panels attached to the platform and        defining sidewalls, a front end wall, a rear end wall, a        ceiling, and a bottom of an oven;    -   (c) a pre-heat zone and a bake zone inside the oven, the        pre-heat zone separated from the bake zone by a shared        (preferably central) internal vertical oven wall, non-insulated,        extending from the front end wall to the rear end wall, and from        the bottom to the ceiling of the oven;    -   (d) one or more pre-heat zone combustion burners and one or more        pre-heat zone recirculation blowers positioned in opposite ends        of the oven in a pre-heat zone combustion/recirculation chamber        positioned in an upper region of the pre-heat zone, and one or        more bake zone combustion burners and one or more bake zone        recirculation blowers positioned in opposite ends of the oven in        a bake zone combustion/recirculation chamber positioned in an        upper region of the bake zone;    -   (e) one or more pre-heat zone heated air supply plenums and one        or more bake zone heated air supply plenums, the plenums fluidly        connected to respective one or more of the recirculation        blowers, the heated air supply plenums comprising        direction-adjustable nozzles attached to a bottom panel thereof,        the heated air supply plenums positioned to direct heated air        through the nozzles and generally downward onto work pieces        traversing through the preheat and bake zones; and    -   (f) one or more return air plenums positioned generally        vertically in each of the pre-heat and bake zones, the one or        more return air plenums each having an air inlet below a level        of the bottom panels of the one or more heated air supply        plenums and an outlet fluidly connected to respective pre-heat        and post bake combustion/recirculation chambers.

Certain systems of this disclosure include those wherein the insulatedbottom panel rests of a top portion of the platform, and the systemfurther comprises pre-heat and bake zone conveyors adapted to transportwork pieces separately through the pre-heat and bake zones, eachconveyor having inlet end and outlet end support sprocket wheelsattached to respective ends of the platform, the sprocket wheels sizedand positioned to allow respective endless belts to pass through therespective pre-heat and bake zones above the insulated bottom of theoven, and between the upper portion of the platform and a lower portionof the platform. In certain systems one or both of the conveyors maycomprise a reversible driver.

Certain systems of this disclosure include those wherein

the one or more pre-heat zone heated air supply plenums comprises asingle plenum,

the one or more bake zone heated air supply plenums comprises a singleplenum, and

the plenums are configured horizontally and co-extensively with theirrespective zones, and parallel to the longitudinal axis of the oven,

each plenum having a decreasing cross-sectional area in the direction ofairflow therethrough,

each plenum fluidly connected to respective outlet ducts of a singlerecirculating air blower in each zone.

Certain systems of this disclosure include those wherein the heated airplenums each comprise a plurality of horizontal sheet metal panels and aplurality of horizontal sheet metal nozzles adjustably attached betweenrespective horizontal sheet metal panels using a plurality of threadedmembers (screws or bolts), the horizontal nozzles adjustable in forwardand rear directions depending on adjustment in and out of the pluralityof threaded members.

Certain systems of this disclosure include an exhaust port for each ofthe pre-heat and bake zones, the exhaust ports fluidly connected to atleast one exhaust fan via corresponding ducts.

Certain systems of this disclosure include those wherein each of thepre-heat and bake zones comprises a curtained inlet vestibule to allowentrance of work pieces, and a curtained outlet vestibule to allow exitof work pieces to, the vestibules configured contain heat and air insidethe oven and maintain low or very low negative pressure (say 1% or 2%vacuum) inside the oven at and near the vestibules. Certain systems ofthis disclosure include those wherein the pre-heat inlet vestibule andthe post bake outlet vestibule are attached to the front end wall, andthe post bake inlet vestibule and the pre-heat outlet vestibule areattached to the rear end wall.

Certain systems of this disclosure include those wherein

the one or more pre-heat zone combustion burners is a single combustionburner in the rear end wall,

the one or more pre-heat zone recirculation blowers is a singlerecirculation blower in the front end wall,

the one or more bake zone combustion burners is a single combustionburner in the rear end wall, and

the one or more bake zone recirculation blowers is a singlerecirculation blower in the front end wall.

Certain systems of this disclosure include those wherein the one or morepre-heat zone combustion burners and the one or more bake zonecombustion burners are nozzle-mixing, gas fired, refractory-lessburners.

Another system embodiment of this disclosure comprises (or consistsessentially of, or consists of):

-   -   (a) a platform, generally rectangular and having longitudinal        axis;    -   (b) a plurality of insulated panels attached to the platform and        defining left and right sidewalls, a front end wall, a rear end        wall, a ceiling, and a bottom of an oven;    -   (c) a pre-heat zone and a bake zone inside the oven, the        pre-heat zone separated from the bake zone by a shared internal        vertical oven wall, non-insulated, extending from the front end        wall to the rear end wall and centrally positioned between the        left and right sidewalls, and extending from the bottom to the        ceiling of the oven;    -   (d) one or more pre-heat zone combustion burners and one or more        pre-heat zone recirculation blowers positioned in opposite ends        of the oven in a pre-heat zone combustion/recirculation chamber        positioned in an upper region of the pre-heat zone, and one or        more bake zone combustion burners and one or more bake zone        recirculation blowers positioned in opposite ends of the oven in        a bake zone combustion/recirculation chamber positioned in an        upper region of the bake zone;    -   (e) one or more pre-heat zone heated air supply plenums and one        or more bake zone heated air supply plenums, the plenums fluidly        connected to respective one or more of the recirculation        blowers, the heated air supply plenums comprising        direction-adjustable nozzles attached to a bottom panel thereof,        the heated air supply plenums positioned to direct heated air        through the nozzles and generally downward onto work pieces        traversing through the preheat and bake zones;    -   (f) one or more return air plenums positioned generally        vertically in each of the pre-heat and bake zones, the one or        more return air plenums each having an air inlet below a level        of the bottom panels of the one or more heated air supply        plenums and an outlet fluidly connected to respective pre-heat        and post bake combustion/recirculation chambers; and    -   (g) separate first and second reversible conveyors positioned to        transport work pieces separately through the pre-heat zone and        bake zone.

Coated pipe couplings made according to one of the methods of thisdisclosure are also considered within this disclosure.

The ovens of the present disclosure are very uniquely designed (despitethe fact that in certain embodiments they may be constructed fromcommonly available components, such as burners, blowers, and standarddesigned insulated oven panels (walls)) to provide a specific airflowpattern about pipe couplings carried by metal baskets, stands, or othercarriers, on conveyors to be used with the oven. In a very generalsense, the ovens of the present disclosure comprise at least twodistinct zones: a raw pipe coupling pre-heat and thermal cleaning zone(referred to herein as simply a “pre-heat zone”), and an uncured, coatedpipe coupling curing zone (referred to herein as simply a “bake zone”).The pipe couplings and containers therefore in part define the airflowpattern in these zones. The ovens of the present disclosure include asource or sources of directly heated fluid (in most embodiments, air,and this will be assumed from here on), the directly heated airincluding combustion gases if combustion burners are the source of heat.The heated air is routed by one or more blowers to internal, generallyhorizontal heated air plenums, and then from the heated air plenumsdownward onto the pipe couplings being carried on conveyor belts, theair being cooled while contacting the pipe couplings. The cooled aircollects in return air plenums positioned along the sides of thepre-heat and bake zones, and is routed generally vertically upward andinto unique combustion/recirculation chambers positioned in the upperregions of the oven, one in the pre-heat zone, and one in the bake zone.In these combustion/recirculation chambers (assuming heat is provided bycombustion burners) each chamber includes one or more combustion burnersexhausting directly into the chamber, typically but not necessarily atone end, and each chamber further includes a recirculation blower,typically but not necessarily at the opposite end) that completes thecycle by blowing the heated air into the hot air plenums. Some of thecooled air is vented through ducts, either by natural draft, or via oneor more exhaust fans, to maintain a slight negative pressure at inletand outlet curtained vestibules on the front and rear ends of the oven.The one or more recirculation blowers in each chamber, and one or moreexhaust blowers may be used to control airflow, providing positive andnegative pressure where needed in the oven. This is a continuous ovenprovided with hot air supply plenums with specially arranged nozzles.

Various terms are used throughout this disclosure. “Direct heating” asused herein means that hot air or combustion gases emanate fromcombustion burners or combustion burner panels, or other heat sources(Joule electric coils) and then intimately mix and combine with,preferably in a flowing fashion to increase heat transfer, one or morestreams of cooled air as described herein. The burners or burner panelsor electric heating coils may be ceiling or wall-mounted (including endwalls and/or side walls), or any combination thereof (for example, twoside wall-mounted burners and one end wall mounted burner panel orelectric heater). Burner panels may form part of an oven ceiling and/orwall structure. A “burner panel” is simply a panel equipped to emit fueland oxidant, or in some embodiments only one of these (for example oneburner panel may only emit fuel, while another burner panel emits onlyoxidant, and vice versa). A “plenum” is a space in which a gas, usuallyair, is contained at a pressure greater than atmospheric pressure.

As used herein the phrase “combustion gases” as used herein meanssubstantially gaseous mixtures comprised primarily of combustionproducts, such as oxides of carbon (such as carbon monoxide, carbondioxide), oxides of nitrogen, oxides of sulfur, and water, as well aspartially combusted fuel, non-combusted fuel, and any excess oxidant.Combustion products may include liquids and solids, for example soot andunburned liquid fuels. “Exhaust”, “burner exhaust”, and “burner fluegas” are equivalent terms and refer to a combination of combustion gasesand other effluent from combustion burners, such as adsorbed water,water of hydration, CO₂ and H₂O liberated from combustion ofhydrocarbons, and the like. Therefore exhaust may comprise oxygen orother oxidants, nitrogen, combustion products (including but not limitedto, carbon dioxide, carbon monoxide, NO_(x), SO_(x), H₂S, and water) anduncombusted fuel.

“Oxidant” as used herein includes air, gases having the same molarconcentration of oxygen as air (for example “synthetic air”),oxygen-enriched air (air having oxygen concentration greater than 21mole percent), and “pure” oxygen grades, such as industrial gradeoxygen, food grade oxygen, and cryogenic oxygen. Oxygen-enriched air mayhave 50 mole percent or more oxygen, and in certain embodiments may be90 mole percent or more oxygen. Primary, secondary, and tertiary oxidantare terms understood in the combustion burner art; burners employedherein may use any one or more of these.

The term “fuel”, according to this disclosure, means a combustiblecomposition comprising a major portion of, for example, methane, naturalgas, liquefied natural gas, propane, butane, hydrogen, steam-reformednatural gas, atomized hydrocarbon oil, combustible powders and otherflowable solids (for example coal powders, carbon black, soot, and thelike), and the like. Fuels useful in the disclosure may comprise minoramounts of non-fuels therein, including oxidants, for purposes such aspremixing the fuel with the oxidant, or atomizing liquid or particulatefuels. As used herein the term “fuel” includes gaseous fuels, liquidfuels, flowable solids, such as powdered carbon or particulate material,waste materials, slurries, and mixtures or other combinations thereof.

The sources of oxidant and fuel may be one or more conduits, pipelines,storage facilities, cylinders, or, in embodiments where the oxidant isair, ambient air. Oxygen-enriched oxidants may be supplied from apipeline, cylinder, storage facility, cryogenic air separation unit,membrane permeation separator, or adsorption unit such as a vacuum swingadsorption unit.

Referring now to the drawings, where the same numerals and letters areused throughout unless otherwise noted, FIG. 1 is a schematic processflow diagram of one method, system, and apparatus embodiment (1) inaccordance with the present disclosure. The dashed line represents theboundary of the oven. It will be realized that the diagram is highlyschematic and is intended to be used in further understanding the moredetailed drawings to follow. Fuel (F) and an oxidant (O) are routed to apre-heat zone combustion/recirculation chamber 55, and a pre-heat zonerecirculation blower 16 routes heated air to a pre-heat zone hot airsupply plenum 68, which in turn routes hot air through a plurality ofgenerally downward-facing nozzles 94 onto baskets or other containersholding pipe couplings on a pre-heat zone conveyor 28. Meanwhile, cooledair is routed to one or more pre-heat zone cooled air plenums 74, asmall amount being vented (V) from the pre-heat zone. Raw pipe couplings(RPC) are routed into the oven and onto pre-heat zone conveyor 28, andafter remaining in the pre-zone for a time and at a temperaturesufficient to thermally clean the RPC, are converted into thermallycleaned pipe couplings (TCPC), which are then routed to a coatingstation 3. Coating station 3 applies a powder or fluid coating (uncured)to the TCPC, and these coated uncured pipe couplings (CUPC) are thenrouted back to the same oven but to a different zone, a bake zone havinga bake zone conveyor 30. Fuel (F) and oxidant (O) are routed into a bakezone combustion/recirculation chamber 59, and a bake zone recirculationblower 18 routes heated air to a bake zone hot air supply plenum 69,which in turn routes hot air through a plurality of generallydownward-facing nozzles 94 onto baskets or other containers holding pipecouplings on a bake zone conveyor 30. Meanwhile, cooled air is routed toone or more bake zone cooled air plenums 84, a small amount being vented(V) from the bake zone.

FIGS. 2 and 3 are schematic right and left perspective views of oneprototype oven embodiment 100 in accordance with the present disclosure.It is deemed a prototype since not all of the components are installed,such as fuel conduits, exhaust fan, and control panel, these items beingillustrated schematically in embodiment 200, FIG. 4. Oven prototypeembodiment 100 includes a platform 2, to which are fastened insulatedpanels forming a right sidewall 4, left sidewall 6, front end wall 8,rear end wall 10, bottom 12, and ceiling or roof 14. Front end and rearend curtained vestibules 20, 22 are illustrated, with front and rearcurtains 24, 26, formed from plastic strips attached to the inside topof the vestibules, and set back a distance from the inlet and exit ofthe vestibules, perhaps 6 to 8 inches. Guards 32, 34 for pre-heat zoneand bake zone recirculation blowers, respectively are illustrated, aswell as a pre-heat zone access door 36 and a bake zone access door 38.Insulated vent ducts for pre-heat zone and bake zone are illustrated at40, 42.

FIG. 4 is a schematic side elevation view of another oven embodiment 200in accordance with the present disclosure, illustrating pre-heat zoneblower motor 17 and support 19, control panel 44, fuel conduits (F),insulation 43 on vent ducts, exhaust fan 70, and exhaust fan motor 72mounted atop the oven. Pre-heat zone combustion burner 54 and air blowertherefore, 56, are also illustrated attached directly to the oven rearend wall 10.

FIGS. 5, 6, and 8 are schematic cross-sectional, plan and rear endelevation views, respectively, with portions cut away to show internalair flow patterns, of embodiment 200. Illustrated are pre-heat zoneinlet 46, pre-heat zone outlet 48, bake zone inlet 50, and bake zone 52,as well as pre-heat zone and bake zone vent passages 49, 51, withdampers 45, 47 illustrated in FIG. 8. The oven has a longitudinal axis(L) as illustrated in FIG. 6. Illustrated in phantom in FIG. 6 are bakezone combustion burner 58 and burner air injection blower 60. Naturalgas or other fuel regulator 62 may be seen schematically in FIG. 5.Various sprocket wheels 64 are illustrated, four for each of conveyors28, 30, and a pair of conveyor driver motors 65, 66, one for eachconveyor.

An important feature of the inventive systems and methods of thisdisclosure is the airflow, and components uniquely designed to producethe airflows in the ovens. One important component is the lower,generally horizontal panel 71, viewable in FIG. 5, which functions asthe lower panel for the pre-heat zone combustion/recirculation chamber,which is defined generally by panel 71, sidewall 4, a portion of(preferably one half of) front end wall 8, and a portion of (preferablyone half of) rear end wall 10, and a partition panel 73 that physicallyseparates the oven into pre-heat zone (PHZ) and bake zone (BZ). Asimilar lower panel, not viewable in FIG. 5, functions as the lowerpanel for the bake zone combustion/recirculation chamber, which isdefined similarly or identically to the pre-heat zonecombustion/recirculation chamber, but for the fact that it is on theother side of partition panel 73. Other important features are theprovision of cooled air return ducts (sometimes simply referred to as“returns”) in the pre-heat and bake zones. The pre-heat zone includescooled air returns 74, 76, 78, 80, and 82, while bake zone includescooled air returns 84, 86, 88, 90, and 92. In embodiment 200, all of thecooled air returns are essentially rectangular boxes having inlets justabove, and on the periphery of their respective conveyors, and outletsopening into their respective combustion/recirculation chamber. In thisway, hot air emanates from nozzles 94 on the bottom of pre-heat zone hotair supply plenum 68, passes around and through raw pipe couplings beingthermally cleaned, and then to the sides and out and up through cooledair returns 74, 76, 78, 80, and 82, as indicated in FIGS. 5 and 6 by thevarious curved single-headed arrows. Simultaneously, hot air emanatesfrom nozzles 94 on the bottom of bake zone hot air supply plenum 69,passes around and through coated, uncured pipe couplings to cure thecoatings, and then to the sides and out and up through cooled airreturns 84, 86, 88, 90, and 92, also as indicated in FIGS. 5 and 6.Small amounts of cooled air from each zone are vented through openings49, 51, in the pre-heat and bake zones, as illustrated. Vent openings49, 51, also draw small amounts of air from around the vestibules, thusmaintaining a slight negative air pressure in the vestibules 20, 22.

FIG. 7 is a detailed plan view of a conveyor roller set useful in thesystems and methods of the disclosure, illustrating side chains 170 androllers 172. As these components are well understood by those skilled inthe conveyor art, their construction is not further detailed, except fortheir materials of construction, which are described herein.

FIG. 9 is an exploded view of a slot nozzle 400 construction useful inthe present ovens and methods. Sheet metal panels 160 of the plenum areprovided, and a set of vertical sheet metal nozzles 162 are attachedthereto with screws 164. The design of the airflow pattern is unique dueto the requirement of circulating air from the combustion/recirculationchambers, through the hot air supply plenums, and then the cooled airreturn plenums back to the combustion/recirculation chambers. The nozzledesign, having lips or projections 166 that protrude out through gap 168between plenum panels 160, was based on having adjustable nozzlescapable of focusing the flow of hot air downward onto and through thepipe couplings. The nozzles were designed and manufactured by EpconIndustrial Systems, LP, The Woodlands, Tex., USA, the assignee of thepresent application. The slot nozzles are attached to the plenum panelsusing sheet metal screws, which allows the nozzles to be adjustedforward or rearward (when the slot nozzles are generally transverse tothe conveyor direction—which is not strictly necessary), depending onthe depth that the screws are driven into their receptacles. Alternativenozzles may be used, such as round nozzles that aredirection-adjustable, such as when they are held by a socket.

FIG. 10 is a detailed cross-section of a wall 500 of the embodiment ofFIGS. 4-6 and 8, featuring insulating material 184, which may be mineralwool, glass wool or other insulating material, for example 6 inch thick8 pound density mineral wool, sandwiched between an external wall panel186, for example 18 gage carbon steel primed and painted, and aninternal wall panel 180, for example aluminized 18 gauge carbon steel orstainless steel, such as 304 or other stainless steel. A thinner layer182, such as 1 inch thick “white blanket” insulation may also beemployed, such as the fiber glass wool insulation known under the tradedesignation THERMORANGE®, available form Owens Corning, Toledo, Ohio,USA. More exotic metals may be used for all or portions of the internalwall panel 180, if desired, such as precious metals and/or noble metals(or alloys). Noble metals and/or other exotic corrosion and/orfatigue-resistant materials include metals such as platinum (Pt),ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os),iridium (Ir), and gold (Au); alloys of two or more noble metals; andalloys of one or more noble metals with a base metal may be employed. Incertain embodiments a protective layer or layers or components maycomprise an alloy attached to a base metal using brazing, welding orsoldering of certain regions.

FIG. 11 is a logic diagram of one method embodiment 600 of treatingmetal pipe couplings in accordance with the present disclosure,comprising the step of continuously moving one or more raw metal pipecouplings through a pre-heat zone of a structure for a time andtemperature sufficient to produce thermally cleaned pipe couplings, andseparately continuously moving thermally cleaned pipe couplings havingan uncured coating applied to at least a portion thereof through aseparate bake zone of the same structure for a time and temperaturesufficient to produce coating-cured pipe couplings (Box 602). Methodembodiment 600 further comprises forming a first heated air stream in apre-heat zone combustion chamber by directly heating air injected intothe pre-heat zone combustion chamber by a first combustion burner, andforming a second heated air stream in a bake zone combustion chamber bydirectly heating air injected into the bake zone combustion chamber by asecond combustion burner (Box 604). Method embodiment 600 furthercomprises flowing the first and second heated air streams intorespective pre-heat zone and bake zone heated air supply plenums, thepre-heat zone heated air supply plenum positioned above the one or moreraw metal pipe couplings moving through the pre-heat zone, the bake zoneheated air supply plenum positioned above the one or more thermallycleaned and uncured coated pipe couplings moving through the bake zone(Box 606). Method embodiment 600 further comprises flowing the first andsecond heated air streams from respective heated air supply plenumsgenerally vertically downward onto the respective pipe couplings movingthrough the respective zones, the first and second heated air streamsflowing into and around the respective one or more pipe couplings, andthen exiting to left and right sides of the respective zones, formingleft and right pre-heat zone cooled air streams and left and right bakezone cooled air streams (Box 608). Method embodiment 600 furthercomprises collecting a major portion of the left and right pre-heat zonecooled air streams in respective left and right pre-heat zone returnducts, flowing the major portion of the left and right pre-heat zonecooled air streams to the pre-heat zone combustion chamber while ventinga minor portion, and collecting a major portion of the left and rightbake zone cooled air streams in respective left and right bake zonereturn ducts, flowing the major portion of the left and right bake zonecooled air streams to the bake zone combustion chamber while venting aminor portion (Box 610).

Certain system and method embodiments may include an incinerator andpollution control section, such as described in my previous U.S. Pat.No. 4,322,203. Briefly, such an incinerator section comprises aninsulated, multi-compartment enclosure having a bottom opening receivingfume-laden air from the oven, such as through the vent conduitspreviously described, or through a separate conduit having an open endfor withdrawing fume-laden air from the oven. The incinerator sectionmay contain conventional heat exchanger and incinerator components, suchas a heat exchanger having two portions for two-stage heat exchange,where the bottom opening communicates with one side of the heatexchanger to conduct fume-laden gases to the other side thereof andthence through a passage to return through the other half of the heatexchanger for discharge into an incinerator unit which includes one ormore burners. The fume-laden air is thus preheated in the heat exchangerprior to entering incinerator unit. The incinerator unit and burner areappropriately sized to burn the hydrocarbon fumes, and other combustiblematter, in the fume-laden air drawn from the oven. The combustion of thecombustible components in the fume-laden air is completed largely in thepassage or chamber described. A combustion chamber opens through anotherpassage extending through the heat exchanger in heat exchange relationwith the fume-laden air passing through the heat exchange conduits.Further details may seen in my previous '203 patent.

“Left” and “right” are arbitrarily chosen as viewed from the front endwall 8 of the structure of embodiment 200 as illustrated schematicallyin FIG. 4.

Suitable heated fluid (preferably hot air) recirculation blowers have acapacity ranging from about 1,000 to about 50,000, CFM, or from about2,000 to about 10,000 CFM, and use an electric motor driver withvariable flow, such as having a power of about 1 to about 10 HP, or fromabout 1 to 5 HP. Such blowers are commercially available, for example,from New York Blower Company, Willowbrook, Ill., U.S.A. Suitable ventair blowers may have a capacity of about 500 to about 5000 standardcubic feet per minute (SCFM), or from about 500 to about 2000 SCFM,driven by a 1 to 5 HP variable frequency drive motor, such as availablefrom New York Blower Company, Willowbrook, Ill., U.S.A.

During operation of embodiments 100, 200 and other embodiments describedherein, the oven pre-heat and bake zones, and plenum internals mayinclude one or more airflow diverters (baffles and the like) foreffecting direct heat exchange from hot air or hot combustion productsto the pipe couplings, or to direct cooled air to thecombustion/recirculation chambers. Airflow diverters may for examplecomprise one or more baffles, distributor plates, grids, and the likefor causing a tortuous flow path. Airflow diverters may take any shape,for example flat plates, corrugated plates, plates having a variety ofprojections or protuberances therefrom such as spikes, knobs, lumps,bumps, and the like, of a variety of sizes, or all the same size. Flowof airstreams is preferably continuous, or at least semi-continuous,while there is a load of pipe couplings being treated in the structure.Airflows may be continued while there are no couplings being treated,but may also be reduced or stopped.

Combustion burners useful in the systems and methods described hereinmay take fuel feed through a primary fuel supply conduit, a fuel primaryflow regulator, which then splits into right side and left side fuelsupply conduits configured to feed right side and left side combustionburners, which also take in air through separate connections, or airblowers if desired. One or more fuel mass flow controllers may beemployed in each fuel supply conduit to each burner. Burners may be, andpreferably are attached directly to front and rear end walls.

The inside structure of heated air supply plenums 68, 69 comprises aseries of slits, holes, and/or other shaped passages (nozzles) allowingthe heated air to escape the plenums downward and travel through andaround the pipe couplings as previously described. The combination ofpositive pressure from recirculation air blowers 16, 18 and reducedpressure induced by exhaust fan 70 aide air flows and allows a cyclicair flow pattern as illustrated.

Methods and systems of the present disclosure may include one or morethermocouples for temperature monitoring and control, NOx sensors,and/or moisture sensors for monitoring and/or control of temperature ofthe pipe coupling treatment, for example using a controller. In certainmethods and systems, control of fuel and/or oxidant may be adjustablewith respect to flow of the fuel or oxidant or both. Adjustment may bevia automatic, semi-automatic, or manual control. A signal may betransmitted by wire or wirelessly from a thermocouple or other sensor toa controller, which may control the method and system by adjusting anynumber of parameters, for example airflow rate may be adjusted throughuse of a signal to one or more air recirculation blowers; one or more offlow rate of fuel and/or oxidant may be adjusted via one or moresignals, it being understood that suitable transmitters and actuators,such as valves and the like, are not illustrated for clarity.

Methods and systems in accordance with the present disclosure may alsocomprise one or more oxy-fuel burners, but as they are only used incertain situations, are more likely to be air/fuel burners. In certainembodiments, all combustion burners and burner panels may be oxy/fuelburners or oxy-fuel burner panels (where “oxy” means oxygen, oroxygen-enriched air, as described earlier), but this is not necessarilyso in all embodiments; some or all of the combustion burners or burnerpanels may be air/fuel burners. Furthermore, heating may be supplementedby electrical (Joule) heating in certain embodiments, in certain zones.Oxy-fuel burners and technologies provide high heat transfer rates, fuelconsumption reductions (energy savings), reduced volume of flue gas, andreduction of pollutant emission, such as oxides of nitrogen (NOx),carbon monoxide (CO), and particulates. Despite the reduction of theflue gas volume that the substitution of combustion air with pure oxygenor oxygen-enriched air yields, a significant amount of energy may belost in the flue gas (also referred to herein as combustion products,exhaust or exhaust gases), especially for high temperature processes. Itwould be advantageous to recover some of the energy available from theflue gas in order to improve the economics of operating an oxy-fuelfired oven. One technique consists in using the energy available in theflue gas to preheat the pipe couplings before loading them into theoven. The energy exchange between the flue gas and the raw pipecouplings may be carried out in a preheater. Other methods may use theheat in the flue gases to heat other fluids or materials useful in atreatment facility, and then use that heat to preheat raw pipecouplings, or fuel or oxidant used in furnaces.

Certain systems, apparatus, and method embodiments of this disclosuremay be controlled by one or more controllers. For example, combustion(flame) temperature may be controlled by monitoring one or moreparameters selected from velocity of the fuel, velocity of the oxidant,mass and/or volume flow rate of the fuel, mass and/or volume flow rateof the oxidant, energy content of the fuel, temperature of the fuel asit enters burners or burner panels, temperature of the oxidant as itenters burners or burner panels, temperature of the effluent (exhaust)at the burner exhaust exit, pressure of the oxidant entering burners orburner panels, humidity of the oxidant, burner or burner panel geometry,combustion ratio, and combinations thereof. Flow diverter positions maybe adjusted or controlled to increase heat transfer in heat transfersubstructures and exhaust conduits.

Various conduits, such as fuel and oxidant supply conduits, exhaustconduits, plenums, partition walls, and airflow ducts of the presentdisclosure may be comprised of metal, ceramic, ceramic-lined metal, orcombination thereof. Suitable metals include carbon steels, stainlesssteels, for example, but not limited to, 306 and 316 steel, as well astitanium alloys, aluminum alloys, and the like. High-strength materialslike C-110 and C-125 metallurgies that are NACE qualified may beemployed for burner body components. (As used herein, “NACE” refers tothe corrosion prevention organization formerly known as the NationalAssociation of Corrosion Engineers, now operating under the name NACEInternational, Houston, Tex.) Use of high strength steel and other highstrength materials may significantly reduce the wall thickness required,reducing weight of the systems and/or space required. In certainlocations, precious metals and/or noble metals (or alloys) may be usedfor portions or all of these conduits. Noble metals and/or other exoticcorrosion and/or fatigue-resistant materials such as platinum (Pt),ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os),iridium (Ir), and gold (Au); alloys of two or more noble metals; andalloys of one or more noble metals with a base metal may be employed. Incertain embodiments a protective layer or layers or components maycomprise an 80 wt. percent platinum/20 wt. percent rhodium alloyattached to a base metal using brazing, welding or soldering of certainregions.

The choice of a particular material for any component is dictated amongother parameters by the chemistry, pressure, and temperature of fuel andoxidant used, size and composition of pipe coupling being treated andtype of product to be produced with certain feedstocks. The skilledartisan, having knowledge of the particular application, pressures,temperatures, and available materials, will be able design the most costeffective, safe, and operable plenums, chambers, exhaust conduits,burners, burner panels, and ovens for each particular applicationwithout undue experimentation.

The total quantities of fuel and oxidant used by burners or burnerpanels of the present disclosure may be such that the flow of oxygen mayrange from about 0.9 to about 1.2 of the theoretical stoichiometric flowof oxygen necessary to obtain the complete combustion of the fuel flow.Another expression of this statement is that the combustion ratio mayrange from about 0.9 to about 1.2. The amount of heat needed to beproduced by combustion of fuel in the burners (and/or Joule heating)will depend upon the efficiency of any preheating of the feedstock. Thelarger the amount of heat transferred to the feedstock, the lower theheat energy required in the oven from the fuel and/or Joule elements.

In burners used in the presently disclosed systems and methods, thevelocity of the fuel in the various burners and/or burner panelembodiments depends on the burner/burner panel geometry used. The upperlimit of fuel velocity depends primarily on the desired temperature ofthe hot combustion gases and the geometry of the burner; if the fuelvelocity is too low, the flame temperature may be too low, providinginadequate temperature in the oven, which is not desired, and if thefuel flow is too high, flame and/or combustion products might impinge ona blower or structural panel, or be wasted, which is also not desired.Similarly, oxidant velocity should be monitored so that flame and/orcombustion products do not impinge on blowers or structural surfaces, orbe wasted. Oxidant velocities depend on fuel flow rate and fuelvelocity. Suitable burners include the nozzle-mixing, gas fired,refractory-less burners known under the trade designation WINNOX, fromEclipse, Inc., and available from Elster Thermal Solutions, Rockford,Ill., U.S.A., and may have a heat output ranging from about 0.5 to about10 million Btu/hr., or from about 0.5 to about 5 million Btu/hr., andhaving a combustion air fan, from 1 to 5 HP. Such burners are able toburn natural gas, propane, and butane, and feature low NOx operationideal for air heating and oven applications, are modular in design,incorporates direct-spark ignition and an air/gas regulator resulting inefficient firing over a wide gas turn down range, all done at acontrolled ratio, producing an intense, short, swirled flame completelycontained within the firing tube. The burner nozzle produces an intensemixing of air and fuel.

A combustion and/or Joule heating process control scheme may beemployed. A master controller may be employed, but the disclosure is notso limited, as any combination of controllers could be used. Thecontroller may be selected from PI controllers, PID controllers(including any known or reasonably foreseeable variations of these), andmay compute a residual equal to a difference between a measured valueand a set point to produce an output to one or more control elements.The controller may compute the residual continuously ornon-continuously. Other possible implementations of the disclosure arethose wherein the controller comprises more specialized controlstrategies, such as strategies selected from feed forward, cascadecontrol, internal feedback loops, model predictive control, neuralnetworks, and Kalman filtering techniques.

The term “control”, used as a transitive verb, means to verify orregulate by comparing with a standard or desired value. Control may beclosed loop, feedback, feed-forward, cascade, model predictive,adaptive, heuristic and combinations thereof. The term “controller”means a device at least capable of accepting input from sensors andmeters in real time or near-real time, and sending commands directly toburner panel control elements, and/or to local devices associated withburner panel control elements able to accept commands. A controller mayalso be capable of accepting input from human operators; accessingdatabases, such as relational databases; sending data to and accessingdata in databases, data warehouses or data marts; and sendinginformation to and accepting input from a display device readable by ahuman. A controller may also interface with or have integrated therewithone or more software application modules, and may supervise interactionbetween databases and one or more software application modules.

The phrase “PID controller” means a controller using proportional,integral, and derivative features. In some cases the derivative mode maynot be used or its influence reduced significantly so that thecontroller may be deemed a PI controller. It will also be recognized bythose of skill in the control art that there are existing variations ofPI and PID controllers, depending on how the discretization isperformed. These known and foreseeable variations of PI, PID and othercontrollers are considered within the disclosure.

The controller may utilize Model Predictive Control (MPC). MPC is anadvanced multivariable control method for use in multiple input/multipleoutput (MIMO) systems. MPC computes a sequence of manipulated variableadjustments in order to optimise the future behavior of the process inquestion. It may be difficult to explicitly state stability of an MPCcontrol scheme, and in certain embodiments of the present disclosure itmay be necessary to use nonlinear MPC. In so-called advanced control ofvarious systems, PID control may be used on strong mono-variable loopswith few or nonproblematic interactions, while one or more networks ofMPC might be used, or other multivariable control structures, for stronginterconnected loops. Furthermore, computing time considerations may bea limiting factor. Some embodiments may employ nonlinear MPC.

A feed forward algorithm, if used, will in the most general sense betask specific, meaning that it will be specially designed to the task itis designed to solve. This specific design might be difficult to design,but a lot is gained by using a more general algorithm, such as a firstor second order filter with a given gain and time constants.

Although only a few exemplary embodiments of this disclosure have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this disclosure. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, no clauses are intended to be inthe means-plus-function format allowed by 35 U.S.C. § 112, Section F,unless “means for” is explicitly recited together with an associatedfunction. “Means for” clauses are intended to cover the structures,materials, and/or acts described herein as performing the recitedfunction and not only structural equivalents, but also equivalentstructures.

What is claimed is:
 1. A method comprising: (a) continuously moving oneor more raw metal pipe couplings through a pre-heat zone of a structurefor a time and temperature sufficient to produce thermally cleaned pipecouplings, and separately continuously moving thermally cleaned pipecouplings having an uncured coating applied to at least a portionthereof through a separate bake zone of the same structure for a timeand temperature sufficient to produce coating-cured pipe couplings; (b)forming a first hot fluid stream in a pre-heat zone hot fluid chamber,and forming a second hot fluid stream in a bake zone hot fluid chamber;(c) flowing the first and second hot fluid streams into respectivepre-heat zone and bake zone hot fluid supply plenums, the pre-heat zonehot fluid supply plenum positioned above the one or more raw metal pipecouplings moving through the pre-heat zone, the bake zone hot fluidsupply plenum positioned above the one or more thermally cleaned anduncured coated pipe couplings moving through the bake zone; (d) flowingthe first and second hot fluid streams from respective hot fluid supplyplenums generally vertically downward onto the respective pipe couplingsmoving through the respective zones, the first and second hot fluidflowing into and around the respective one or more pipe couplings, andthen exiting to left and right sides of the respective zones, formingleft and right pre-heat zone cooled fluid streams and left and rightbake zone cooled fluid streams; and (e) collecting a major portion ofthe left and right pre-heat zone cooled fluid streams in respective leftand right pre-heat zone return ducts, flowing the major portion of theleft and right pre-heat zone cooled fluid streams to the pre-heat zonehot fluid chamber while venting a minor portion, and collecting a majorportion of the left and right bake zone cooled fluid streams inrespective left and right bake zone return ducts, flowing the majorportion of the left and right bake zone cooled fluid streams to the bakezone hot fluid chamber while venting a minor portion, wherein theventing of the minor portions comprises exhausting minor portions of thecooled streams at a rate and amount sufficient to maintain a negativepressure in and near inlet and outlet vestibules of the pre-heat andbake zones.
 2. The method of claim 1 wherein the hot fluid streams arehot combustion products, and the hot fluid chambers are combustionchambers, and the hot combustion products are formed by combusting oneor more fuels with one or more oxidants in one or more combustionburners attached to the structure externally of the respectivecombustion chambers, the one or more combustion burners exhaustingdirectly into the respective combustion chambers.
 3. The method of claim2 wherein the forming a first hot combustion product comprises forming adirectly heated air, oxygen-enriched air, or oxidant stream in thepre-heat zone combustion chamber by directly heating air,oxygen-enriched air, or oxidant injected into the pre-heat zonecombustion chamber by a first combustion burner, and the forming asecond hot combustion product comprises forming a directly heated air,oxygen-enriched air, or oxidant stream in the bake zone combustionchamber by directly heating air, oxygen-enriched air, or oxidantinjected into the bake zone combustion chamber by a second combustionburner.
 4. The method of claim 2 wherein the fuel is natural gas, theoxidant is air, and the first and second hot combustion product streamsare first and second directly heated air streams.
 5. The method of claim1 wherein steps (b)-(e) are continuous and are carried outsimultaneously with step (a).
 6. The method of claim 1 wherein step (a)comprises continuously moving one or more raw metal pipe couplingsthrough the pre-heat zone of the structure horizontally, and separatelycontinuously moving the thermally cleaned pipe couplings having anuncured coating applied to at least a portion thereof through theseparate bake zone of the same structure horizontally, both continuousmovements being parallel to a longitudinal axis of the structure.
 7. Themethod of claim 6 wherein the horizontal movements are in oppositedirections.
 8. The method of claim 1 wherein the fuel is selected fromthe group consisting of methane, gaseous natural gas, liquefied naturalgas, propane, butane, hydrogen, steam-reformed natural gas, atomizedhydrocarbon oil, combustible powders, flowable solids, waste materials,slurries, and mixtures or other combinations thereof, and the oxidant isselected from the group consisting of air, gases having the same molarconcentration of oxygen as air, oxygen-enriched air having 50 molepercent or more oxygen, industrial grade oxygen, food grade oxygen, andcryogenic oxygen.
 9. The method of claim 1 wherein the time andtemperature sufficient to produce thermally cleaned pipe couplingsranges from about 1 to about 4 hours at temperature ranging from about600° F. to about 800° F., and the time and temperature sufficient toproduce cured coatings ranges from about 1 to about 4 hours attemperature ranging from about 350° F. to about 550° F.
 10. The methodof claim 2 comprising controlling thermal cleaning of the one or morepipe couplings by one or more control methods selected from the groupconsisting of monitoring composition of the vented fluid from thepre-heat zone, temperature of the pre-heat zone combustion chamber,temperature of raw pipe couplings moving though the pre-heat zone, fueland/or oxidant flow rate to the one or more pre-heat zone combustionburners, rate of moving the raw pipe couplings thought the pre-heatzone, and combinations thereof, and controlling baking of the coating ofthe one or more pipe couplings by one or more control methods selectedfrom the group consisting of monitoring composition of vented fluid fromthe bake zone, temperature of the bake zone combustion chamber,temperature of thermally cleaned and uncured coated pipe couplingsmoving though the bake zone, fuel and/or oxidant flow rate to the one ormore bake zone combustion burners, rate of moving the thermally cleaneduncured coated pipe couplings thought the bake zone, and combinationsthereof.
 11. A method comprising: (a) continuously moving one or moreraw metal pipe couplings through a pre-heat zone of a structure for atime and temperature sufficient to produce thermally cleaned pipecouplings, and separately continuously moving thermally cleaned pipecouplings having an uncured coating applied to at least a portionthereof through a separate bake zone of the same structure for a timeand temperature sufficient to produce coating-cured pipe couplings; (b)forming a first heated air stream in a pre-heat zone combustion chamberby directly heating air injected into the pre-heat zone combustionchamber by a first combustion burner, and forming a second heated airstream in a bake zone combustion chamber by directly heating airinjected into the bake zone combustion chamber by a second combustionburner; (c) flowing the first and second heated air streams intorespective pre-heat zone and bake zone heated air supply plenums, thepre-heat zone heated air supply plenum positioned above the one or moreraw metal pipe couplings moving through the pre-heat zone, the bake zoneheated air supply plenum positioned above the one or more thermallycleaned and uncured coated pipe couplings moving through the bake zone;(d) flowing the first and second heated air streams from respectiveheated air supply plenums generally vertically downward onto therespective pipe couplings moving through the respective zones, the firstand second heated air streams flowing into and around the respective oneor more pipe couplings, and then exiting to left and right sides of therespective zones, forming left and right pre-heat zone cooled airstreams and left and right bake zone cooled air streams; and (e)collecting a major portion of the left and right pre-heat zone cooledair streams in respective left and right pre-heat zone return ducts,flowing the major portion of the left and right pre-heat zone cooled airstreams to the pre-heat zone combustion chamber while venting a minorportion, and collecting a major portion of the left and right bake zonecooled air streams in respective left and right bake zone return ducts,flowing the major portion of the left and right bake zone cooled airstreams to the bake zone combustion chamber while venting a minorportion, wherein the venting of the minor portions comprises exhaustingminor portions of the cooled streams at a rate and amount sufficient tomaintain a negative pressure in and near inlet and outlet vestibules ofthe pre-heat and bake zones.
 12. Coating-cured pipe couplings madeaccording to the method of claim
 1. 13. Coating-cured pipe couplingsmade according to the method of claim 11.